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Grass Weathers Wake

The wake of a new Alameda-San Francisco ferry has not damaged eel grass beds off the East Bay Island, at least not according to data from the first year of monitoring. Wildlife agencies and environmental groups were concerned that the wake would erode these highly productive underwater ecosystems - eel grass beds can sustain up to 100 times more shrimps, snails and other organisms than surrounding areas, according to Dr. Chris Kitting of California State University at Hayward. Concerned groups also worried that the ferry might stir up bottom sediments - eel grass grows just a few meters below the surface and needs light.

"There has been typical growth," says Tom Keegan of Entrix, the company commissioned to do the monitoring. Their study continues through 1994, and will help officials determine whether to continue the ferry's conditional-use permit.

Only 316 acres of eel grass remain in the Bay, and the Alameda beds help feed the endangered California least tern colony nearby. The tern dives in the beds for Northern anchovy, topsmelt and Pacific herring, which lay eggs in the grass. Eel grass itself - a plant whose bright-green buoyant blades sway with tides and currents like meadow grasses in a breeze - is also vulnerable to extinction in the Bay.

Entrix split the beds up into transects, and measured density, grass blade length and flowering stocks both near the ferry channel and farther away, as a control. So far, the seasonal testing indicates nothing more than normal variation, according to Keegan.

Contact: Tom Keegan (510)935-9920

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